1. Field of the Invention
The present invention relates to a rare probability connection call registration method using payload type indication (PTI) field information for an asynchronous transfer mode (ATM) switching system, and in particular to an improved rare probability connection call registration method using PTI field information for an ATM switching system which is capable of registering a rare probability connection call (RPCC) by using PTI field information which indicates the congestion of the switching component within the cell header, whereby it is possible to more quickly control the network and restrict an ineffective call, thus maximizing the efficiency of the network.
2. Description of the Conventional Art
Most traffic congestion of a communication network occurs due to an overload in a receiving system. This communication congestion or the overload of the switching system occurs due to natural disasters, an overload phenomenon of the system when a multitude of call services are requested at one time, or communication traffic concentrated on a specific receiving system due to an unexpected communication failure.
When calls are concentrated at a predetermined time with respect to a specific receiving system (for example, reservations for a public performance, or the audience rating response to a television program), the above-described heavy call concentration phenomenon may occur even though an operator of the switching system predicts such heavy call congestion if special operations on the system are not made.
When call requests are heavily concentrated on a predetermined receiving number, that is when many calls are concentrated at one time on the destination number beyond the design specification of the connection admission control function, the system can only offer limited service, and the system may go down due to the above-described problems.
FIG. 4 is a graph illustrating a performance variation when a switching system is overloaded.
As shown therein, the curved line indicates a theoretical system performance which is obtainable when an overload of the system or traffic congestion occurs, and the curved line "c" denotes system performance when the congestion control function is not operated, and the curved line "b" denotes affordable system performance when the congestion control function is operated.
If the above-described situation is continuously maintained, the system congestion resulting from many call attempts to a specific number may cause further congestion with respect to the neighboring system. So, finally, there is the possibility of system-wide failure.
In order to overcome the above-described problems, a conventional public switched telephone network (PSTN) is directed to check a traffic completion ratio with respect to a candidate code (traffic received in a specific code of a predetermined system) that the operation input, and when a call completion ratio of a corresponding code is less than a predetermined threshold value, the call with respect to the corresponding code is controlled.
Such, method is directed to maximizing the efficiency of the network so that system resources may be evenly distributed for a call except for a congested call by detecting a receiving code for which the call completion ratio is lower than that of a normal call, and controlling the receiving code in a transmitter for which a desired call attempt is possible or the switching system near a transmitting terminal. A call for which the completion ratio is lower than that of a normal call is called a rare probability of a connection call (RPCC).
In the case of the conventional PSTN, control with respect to the code in which the call completion ratio is significantly lower due to the congestion of a specific switching system is performed based on a result of the statistic function after a lapse of a predetermined time after the congestion occurred, so that a large amount of time is required for performing the control, and since the call completion ratio is controlled only by statistic data, if faults in the statistic function error occurs, an error may occur in the system.
In addition, when performing a function based on the candidate code, since the control is performed after a predetermined time after the operator inputs a predetermined code has elapsed, it is impossible to prevent call concentration problems due to an unpredictable and sudden failure of the system in conventional methods.